import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;

/**
 * UDP回显服务器
 */
public class UdpEchoServer {
    private DatagramSocket socket = null;

    public UdpEchoServer(int port) throws SocketException {
        socket = new DatagramSocket(port);
    }

    //启动服务器
    public void start() throws IOException {
        System.out.println("服务器启动");
        while (true) {
            //1.读取客户端发来的请求
            DatagramPacket requestPacket = new DatagramPacket(new byte[4096],4096);
            socket.receive(requestPacket);
            String request = new String(requestPacket.getData(),0,requestPacket.getLength());
            //2.根据请求,做出响应
            String response = process(request);
            //这里是回显服务器,就返回客户端发来的请求
            DatagramPacket responsePocket = new DatagramPacket(response.getBytes(),response.getBytes().length,
                    requestPacket.getAddress(),requestPacket.getPort());
            socket.send(responsePocket);
            System.out.printf("[%s,%d] req: %s,resp: %s\n",requestPacket.getAddress().toString(),requestPacket.getPort(),
                    request,response);
        }
    }

    public String process(String request){
        return request;
    }

    public static void main(String[] args) throws IOException {
        UdpEchoServer udpEchoServer = new UdpEchoServer(9090);
        udpEchoServer.start();

    }
}
